During the 20 th century cities are becoming less dense. They are sprawling which leads to the loss of surrounding natural land, as urban development spreads rapidly into previously productive or environmentally significant land, as well as increasing concerns about the environmental effects of automobile emissions in relation to climate change and the negative social impacts. But since we live in a free market economy the most important arguments against sprawl are the economic impacts of it.

Sprawl is not cost-effective and sustainable. Moving from urban sprawl to a ‘compact city’ has been proposed as one way urban sustainability can be improved upon. How compact the cities should be? I found a graph which illustrates the most efficient density from the viewpoint of infrastructure costs. (The quality is not good but it is the best I could find)

Photo by Andis Kublačovs

According to this graph the most cost-efficient use of infrastructure is when the density of population is 800 - 1000 inhabitants/ha. Which means 80 000 - 100 000 inhabitants/km2. This number was reached or exceeded in Rome 2000 years ago, Paris and London 200 years ago and Manhattan at the beginning of this century. Such a density reduces the comfort and quality of life in city. Cities will never be as dense as before. If we take a look at the overcrowded cities worldwide we see that no one is as dense. And people do not want as dense cities. Such a density was one of the reasons that caused sprawl in the first place.

Let’s take a look at the city I live in. According to the official website of Riga municipality in 2008 there were 2322 inhabitants/km2 in Riga which is average number for city in Europe. If we compare the number with the cities of America and Australia it seems quite sustainable. Is it enough? Thedensification could be done by recycling obsolete industrial land. But how much denser the city should be?

Some researchers counter that raising densities results in more expensive real estate, greater road congestion and more air pollution. And the question remains – How dense is sustainable city?